A well system, such as an oil or gas well, can include a wellbore drilled through a subterranean formation for extracting hydrocarbons from the subterranean formation. The wellbore can include a casing string to prevent the walls of the wellbore from caving in. Well tools can be inserted into the casing string to perform operations, such as drilling operations, in the wellbore. But the casing string can become damaged as the well tools are positioned within the casing string and perform operations within the casing string.